The present invention relates to the field of angioplasty. In particular, the present invention relates to a balloon dilatation catheter which allows blood to passively flow past an inflated balloon during a prolonged dilatation of a blood vessel.
Angioplasty has gained wide acceptance as an efficient, effective and alternative method of removing undesirous restrictions caused by tissue growth or lesions on an inner wall of a blood vessel. Such tissue growth or lesions cause a narrowing of the blood vessels called a "stenosis," which severely restricts or limits the flow of blood. In the most widely used form of angioplasty, a catheter shaft, which has an inflatable balloon at its distal end, is guided through the vascular system. With the aid of fluoroscopy, a physician is able to position the balloon across the stenosis. The balloon is then inflated by applying fluid pressure through an inflation lumen of the catheter to the balloon. Inflation of the balloon compresses the stenosis-causing lesion thereby reestablishing an acceptable blood flow through the artery.
One disadvantage of many dilatation catheters of the prior art is the complete occlusion of the blood vessel that results while the balloon is inflated. Prolonged complete blockage of a coronary artery causes patient discomfort and poses serious risk of damage to the tissue downstream from the occlusion which is deprived of oxygenated blood. These consequences pose a severe limitation on the length of time the balloon can remain inflated within the artery to effectively remove the stenosis.
Various methods for providing passive perfusion of blood through or past the inflated balloon are found in the following prior art references: Baran et al. U.S. Pat. No. 4,423,725; Sahota U.S. Pat. No. 4,581,017; Hershenson U.S. Pat. No. 4,585,000; Horzewski et al. U.S. Pat. No. 4,771,777; Mueller et al. U.S. Pat. No. 4,790,315; Songer et al. U.S. Pat. No. 4,892,519; Goldberger U.S. Pat. No. 4,909,252; Sogard et al. U.S. Pat. No. 4,944,745; Sahota U.S. Pat. No. 4,983,167 and European Patent Application 0 246 998; Boussignac et al. U.S. Pat. No. 5,000,734; Patel U.S. Pat. No. 5,000,743; and Bonzel U.S. Pat. No. 5,002,531.
Perfusion catheters comprised of a single tubular shaft including two side-by-side lumens, one for inflation of the balloon and one for carrying blood past the balloon, exhibit limited flexibility. A dividing wall, which is a common element of a side-by-side dual lumen tubular shaft, stiffens the shaft and detracts from the flexibility necessary for essential steerability characteristics. Perfusion catheter shafts comprised of equal length, coaxial outer and inner tubes must possess sufficient space to accommodate inflation fluid, a guide wire and an adequate volume of blood. In order to satisfy these requirements, the outer diameter of such a shaft must be relatively large at the distal end of the shaft. This inhibits the ability of coaxial, multitubular perfusion catheter shafts from traversing relatively narrow stenoses.
There is still a need in the field for a perfusion dilation catheter shaft that is capable of being readily pushable at the proximal end, flexible and maneuverable along a substantial length of the shaft and relatively narrow at the distal end without sacrificing flow space for blood past an inflated balloon.